Most nonclinicalKlebsiella strains are notK. pneumoniae sensu stricto

Twenty-nine bacterial isolates identified by routine biochemical procedures asKlebsiella pneumoniae and included in a recent numerical, taxonomy study were analyzed for molecular heterogeneity by DNA hybridization competition experiments. The isolates were obtained from clinical sources, from potable drinking water, trees, sawdust, pulp mill environs, and fresh vegetables. Three distinct groups were formed based on hybridization levels to three reference, cultures. One group exhibited 73–100% relative reassociation (RR) to a fecal coliform-positive reference, organism; a second group exhibited 60–100% RR to a fecal coliform-negative reference culture, while the third group exhibited 84–100% RR to an indole-producing, pectate-degrading, fecal coliformnegative reference, culture. The first group is designated asK. pneumoniae sensu stricto, and the third group asK. oxytoca. The, other isolates comprise at least one, and perhaps three additionalKlebsiella species. The present groups correlate, well with a numerical taxonomy study and with a biotyping scheme, which illustrated that mostK. pneumoniae sensu stricto are of clinical origin,Klebsiella “species” are primarilly of nonclinical orgin, andK. oxytoca are found in both environments. The fecal coliform test response is relevant in the genusKlebsiella for both taxonomic and ecological information in assessing the origin and health significance ofKlebsiella strains derived from nonclinical sources.